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Biomedical subjects

Satoshi Omura

Publications and source records attributed to Satoshi Omura.

At least 19 recordsLinked to original sources
PubMed2003

Cytochrome p450 complement (CYPome) of the avermectin-producer Streptomyces avermitilis and comparison to that of Streptomyces coelicolor A3(2).

The genus Streptomyces produces about two-thirds of naturally occurring antibiotics and a wide array of other secondary metabolites, including antihelminthic agents, antitumor agents, antifungal agents, and herbicides. The newly completed genome sequence of the avermectin-producing bacterium Streptomyces avermitilis contains 33 cytochromes p450 (CYPs), many more than the 18 observed in Streptomyces coelicolor A3(2). Some of the likely metabolic functions are reported together with their genomic location and bioinformatic analysis. Seven entirely new CYP families were found together with close homologues of some forms observed in S. coelicolor A3(2). The presence of unusual CYP forms associated with conservons is revealed and of these, CYP157 forms in both S. avermitilis and S. coelicolor A3(2) deviate from the previously accepted rule for an EXXR motif within the K-helix of CYPs. Amongst this range of CYPs are forms associated with avermectin, filipin, geosmin, and pentalenolactone biosynthesis as well as unknown pathways of secondary metabolism.

Chromosomes, Fungal↗
PubMed2003

Complete genome sequence and comparative analysis of the industrial microorganism Streptomyces avermitilis.

Species of the genus Streptomyces are of major pharmaceutical interest because they synthesize a variety of bioactive secondary metabolites. We have determined the complete nucleotide sequence of the linear chromosome of Streptomyces avermitilis. S. avermitilis produces avermectins, a group of antiparasitic agents used in human and veterinary medicine. The genome contains 9,025,608 bases (average GC content, 70.7%) and encodes at least 7,574 potential open reading frames (ORFs). Thirty-five percent of the ORFs (2,664) constitute 721 paralogous families. Thirty gene clusters related to secondary metabolite biosynthesis were identified, corresponding to 6.6% of the genome. Comparison with Streptomyces coelicolor A3(2) revealed that an internal 6.5-Mb region in the S. avermitilis genome was highly conserved with respect to gene order and content, and contained all known essential genes but showed perfectly asymmetric structure at the oriC center. In contrast, the terminal regions were not conserved and preferentially contained nonessential genes.

Amino Acid Sequence↗
PubMed2003

Total synthesis and adjuvant activity of all stereoisomers of pinellic acid.

Pinellic acid is a novel and potentially useful oral adjuvant when used in conjunction with intranasal inoculation of influenza HA vaccines. All stereoisomers of pinellic acid have been synthesized via regioselective asymmetric dihydroxylation, regioselective inversion, and stereoselective reduction, and their adjuvant activities were characterized. Among this series of isomers, 9S, 12S, 13S compound has the most potent adjuvant activity. Structure-activity relationships are discussed.

Adjuvants, Immunologic↗
PubMed2003

Atpenins, potent and specific inhibitors of mitochondrial complex II (succinate-ubiquinone oxidoreductase).

Enzymes in the mitochondrial respiratory chain are involved in various physiological events in addition to their essential role in the production of ATP by oxidative phosphorylation. The use of specific and potent inhibitors of complex I (NADH-ubiquinone reductase) and complex III (ubiquinol-cytochrome c reductase), such as rotenone and antimycin, respectively, has allowed determination of the role of these enzymes in physiological processes. However, unlike complexes I, III, and IV (cytochrome c oxidase), there are few potent and specific inhibitors of complex II (succinate-ubiquinone reductase) that have been described. In this article, we report that atpenins potently and specifically inhibit the succinate-ubiquinone reductase activity of mitochondrial complex II. Therefore, atpenins may be useful tools for clarifying the biochemical and structural properties of complex II, as well as for determining its physiological roles in mammalian tissues.

Animals↗
PubMed2003

Isolation of new actinomycete strains for the screening of new bioactive compounds.

In order to facilitate the discovery of novel bioactive compounds from microorganisms, various techniques for isolation of new actinomycete strains have been attempted. Studies of the vertical distribution of actinomycetes in soil, isolation of actinomycetes from desert soils or fallen leaves, selective isolation of Kitasatospora strains using novobiocin or Actinoplanes strains using the chemotactic method, and the use of gellan gum as a solidifying agent were carried out. We discovered 9 novel bioactive compounds from actinomycete strains isolated under unusual conditions, and proposed two new genera, five new species and one new subspecies.

Actinobacteria↗
PubMed2003

Core structure in roselipins essential for eliciting inhibitory activity against diacylglycerol acyltransferase.

Fungal roselipins, discovered as inhibitors of diacylglycerol acyltransferase (DGAT), consist of three parts; highly methylated C20 fatty acid, mannose and arabinitol. Demannosyl and/or dearabinitoyl roselipins were prepared chemically or enzymatically. Demannnosyl roselipins conserved the DGAT inhibitory activity, but the others lost the activity, indicating that the arabinitoyl fatty acid core is essential for eliciting the activity.

Acyltransferases↗
PubMed2003

Takanawaenes, novel antifungal antibiotics produced by Streptomyces sp. K99-5278. I. Taxonomy, fermentation, isolation and biological properties.

Three new pentaene macrolides having a 28-membered ring, designated takanawaenes A, B and C, were isolated from the fermentation broth of Streptomyces sp. K99-5278 by solvent extraction, silica-gel column chromatography and HPLC. Takanawaenes showed antifungal activity against Aspergillus niger, Mucor racemosus, Candida albicans and Saccharomyces cerevisiae.

Antifungal Agents↗
PubMed2003

New monordens produced by amidepsine-producing fungus Humicola sp. FO-2942.

Based on UV spectrum-guided purification, new monordens C, D and E, known monordens A (radicicol) and B and 5-O-methylsclerone were isolated from the fermentation broth of amidepsine-producing Humicola sp. FO-2942 by solvent extraction, silica-gel column chromatography, ODS column chromatography and HPLC. All monordens cause the cell cycle arrest at G1 and G2/M phases in Jurkat cells. But among them, monordens A and E show antifungal activity only against Aspergillus niger.

Antifungal Agents↗
PubMed2003

Structure elucidation of new monordens produced by Humicola sp. FO-2942.

Structures of three novel compounds designated monordens C to E, isolated from the fermentation broth of amidepsine-producing fungus Humicola sp. FO-2942, were elucidated by spectroscopic evidence. Monordens C is 6,7-dihydromonorden A. Monordens D and E lack the epoxide moiety of monordens C and B, respectively.

Antifungal Agents↗
PubMed2002

Suppression of bone resorption by madindoline A, a novel nonpeptide antagonist to gp130.

IL-6 is a multifunctional cytokine involved in regulation of differentiation, antibody production, and growth of certain types of tumor cells. Its excessive production plays a major role in pathogenesis of multiple myeloma and postmenopausal osteoporosis. In the course of a screening program aimed at IL-6 inhibitor from microbial products, we found madindoline A (MDL-A) and madindoline B, which have a fuloindoline structure with diketocyclopentene bound to the methyl group. MDL-A has no cytotoxic activities. It inhibited only activities of both IL-6 and IL-11 without affecting the IL-6-specific signal transduction cascade, JAK2/STAT3. In a dose-dependent manner [(3)H]MDL-A binds to gp130, which is a signal transducing 130-kDa glycoprotein, but formation of the trimeric complex IL-6/IL-6 receptor/gp130 was not inhibited, suggesting that MDL-A suppresses dimerization of trimeric complexes. Not only did MDL-A markedly inhibit IL-6- and IL-11-induced osteoclastogenesis in vitro, but it also inhibited IL-6-stimulated serum amyloid A production and bone resorption in an experimental model of postmenopausal osteoporosis in vivo by a different mechanism from that of 17beta-estradiol. Here we show that MDL-A has a highly selective inhibitory effect on IL-6 and IL-11 activities by inhibiting a gp130 activity while suppressing bone loss in ovariectomized mice. MDL-A is anticipated as a lead compound for treatment of hormone-dependent postmenopausal osteoporosis, which has no serious side effects, and as a new mechanism of action, gp130 blocking.

Animals↗
PubMed2002

Remarkable influence of the aromatic substructure in 9-methoxystrobilurin derivatives on their antifungal activity.

9-Methoxystrobilurin-type beta-methoxyacrylate antibiotics (MOSBs) having various aromatic substructures were synthesized. The antifungal activity of the synthesized MOSBs against pathogenic and non-pathogenic fungi was examined, and the obtained results revealed that the antifungal activity of MOSBs was highly dependent on the aromatic substructures. However, no significant correlation was observed between cytotoxicity against human fibroblasts-like cell line and their structural properties. In addition, our results suggested that the strong growth-inhibitory activity of 9-methoxystrobilurin K against human-derived cell lines should be related to its hindered ether-type substructure.

Acrylates↗
PubMed2002

Accelerated degradation of mislocalized UDP-glucuronosyltransferase family 1 (UGT1) proteins in Gunn rat hepatocytes.

Gunn rat is a hyperbilirubinemic rat strain that is inherently deficient in the activity of UDP-glucuronosyltransferase form 1A1 (UGT1A1). A premature termination codon is predicted to produce truncated UGT1 proteins that lack the COOH-terminal 116 amino acids in Gunn rat. Pulse-chase experiments using primary cell cultures showed that the truncated UGT1A1 protein in Gunn rat hepatocytes was synthesized similarly to wild-type UGT1A1 protein in normal Wistar rat hepatocytes. However, the truncated UGT1A1 protein was degraded rapidly with a half-life of about 50 min, whereas the wild-type UGT1A1 protein had a much longer half-life of about 10 h. The rapid degradation of truncated UGT1A1 protein was inhibited partially but not completely by treating Gunn rat hepatocytes with proteasome inhibitors such as carbobenzoxy-Leu-Leu-leucinal and lactacystin. By contrast, neither the lysosomal cysteine protease inhibitor nor the calpain inhibitor slowed the degradation. Our findings show that the absence of UGT1 protein from Gunn rat hepatocytes is due to rapid degradation of the truncated UGT1 protein by the proteasome and elucidate the molecular basis underlying the deficiency in bilirubin glucuronidation.

Acetylcysteine↗
PubMed2002

High-resolution structures of a chitinase complexed with natural product cyclopentapeptide inhibitors: mimicry of carbohydrate substrate.

Over the past years, family 18 chitinases have been validated as potential targets for the design of drugs against human pathogens that contain or interact with chitin during their normal life cycles. Thus far, only one potent chitinase inhibitor has been described in detail, the pseudotrisaccharide allosamidin. Recently, however, two potent natural-product cyclopentapeptide chitinase inhibitors, argifin and argadin, were reported. Here, we describe high-resolution crystal structures that reveal the details of the interactions of these cyclopeptides with a family 18 chitinase. The structures are examples of complexes of a carbohydrate-processing enzyme with high-affinity peptide-based inhibitors and show in detail how the peptide backbone and side chains mimic the interactions of the enzyme with chitooligosaccharides. Together with enzymological characterization, the structures explain why argadin shows an order of magnitude stronger inhibition than allosamidin, whereas argifin shows weaker inhibition. The peptides bind to the chitinase in remarkably different ways, which may explain the differences in inhibition constants. The two complexes provide a basis for structure-based design of potent chitinase inhibitors, accessible by standard peptide chemistry.

Animals↗
PubMed2002

Macrosphelide B suppressed metastasis through inhibition of adhesion of sLe(x)/E-selectin molecules.

Macrosphelide B (MSB), a 16-membered macrolide from Microsphaeropsis sp. FO-5050, inhibits adhesion of sialyl Lewis(x) (sLe(x))-expressing HL-60 cells to LPS-activated (E-selectin-expressing) human umbilical vein endothelial cells (HUVECs) in vitro. This study examines MSB effects on metastasis of B16/BL6 mouse melanoma cells (B16/BL6 cells) and L5178Y-ML mouse lymphoma cells in vivo and analyzes the MSB antimetastatic activity mechanism. When administered MSB at 20 mg/kg/day, lung metastatic nodules of B16/BL6 cells were significantly decreased (T/C = 45%). However, no inhibition of metastasis of L5178Y-ML cells to the spleen and liver was observed. Flow cytometry analysis showed that B16/BL6 cells expressed high levels of sLe(x) antigen, whereas expression on L5178Y-ML cells was low. Under in vitro conditions, B16/BL6 cells demonstrated a greater degree of adhesion to LPS-activated HUVECs than L5178Y-ML cells, but adhesion was significantly inhibited by MSB and sLe(x) antibody. Combined therapy of MSB and cisplatin (CDDP) induced remarkable lung metastasis inhibition without adverse effects of CDDP to the host. All these findings suggest that MSB suppresses lung metastasis of B16/BL6 cells by inhibiting cell adhesion to endothelial cells through the sLe(x) molecule.

Animals↗
PubMed2002

Short total synthesis of (+)-madindolines A and B.

[reaction: see text] A short and efficient total synthesis of (+)-madindolines A (1) and B (2), potent and selective inhibitors of interleukin 6, has been achieved. The synthesis features a key chelation-controlled 1,4-diastereoselective acylation to generate the quaternary carbon and an intramolecular acylation of allylsilane to build up the cyclopentene unit.

Bridged Bicyclo Compounds, Heterocyclic↗